1. Field of the Invention
The present invention relates to a video signal producing apparatus and a video signal producing method in which a composite video signal used for a television set or a video tape recorder is produced.
2. Description of Related Art
A display principal of a Braun tube used in a television set is initially described in brief.
In a television set, an electron beam is moved in horizontal and vertical directions to display an image on an image plane of a Braun tube. The movement of the electron beam in the horizontal direction is called a horizontal scanning, and the movement of the electron beam from top to bottom is called a vertical scanning. Also, when the horizontal scanning and the vertical scanning are simultaneously performed in the Braun tube, a number of fine loci extending in the horizontal direction appear on the image plane. Each locus is called a horizontal scanning line.
A plurality of broadcast systems for the color television are known, and regulations of National Television System Committee (NTSC) are adopted in Japan. In the NTSC, 525 horizontal scanning lines are used to display a frame-image on the image plane for each frame, and 30 frame-images are sent to the Braun tube every second. In practical use, to suppress the flickering occurring in the frame-images, the 525 horizontal scanning lines of each frame-image is divided into two groups of 262.5 horizontal scanning lines alternately arranged in the 525 horizontal scanning lines to produce two rough images respectively composed of one group of 262.5 horizontal scanning lines from each frame-image (refer to FIG. 10B), and 60 rough images are displayed every second. This scanning is called an interlacing scanning, and each rough image composed of the 262.5 horizontal scanning lines corresponds to one field. The rough image composed of 262.5 horizontal scanning lines numbered by lower serial numerals is called an odd field, and the rough image composed of 262.5 horizontal scanning lines numbered by higher serial numerals is called an even field. The odd and even fields are interlaced with each other for each frame. As shown in FIG. 10B, one odd field is displayed by 262.5 horizontal scanning lines indicated by solid lines, one even field is displayed by 262.5 horizontal scanning lines indicated by broken lines, and the odd fields and the even fields are alternately displayed.
In the horizontal scanning, a horizontal retrace blanking period is provided after the completion of each horizontal scanning. Also, in the vertical scanning, a vertical retrace blanking period is provided after the completion of each vertical scanning. In each retrace blanking period, the electron beam is cut. Therefore, as shown in FIG. 10A, neither horizontal retrace line nor vertical retrace line is displayed on the image plane.
In each horizontal retrace blanking period, a horizontal synchronizing signal Hsync is arranged to determine a starting position of the horizontal scanning line. Also, a vertical synchronizing signal Vsync is arranged in each vertical retrace blanking period to determine a starting position of the vertical scanning.
The beam operation performed for displaying an image on the image plane of the Braun tube is controlled according to a composite video signal produced in a video processing circuit. In the composite video signal, information of scanning lines, information of the horizontal retrace blanking periods, information of the vertical retrace blanking period, information of the horizontal synchronizing signals, information of the vertical synchronizing signal, field information, and image information (color information and luminance information) are included for each field. In a video tape recorder (called VTR), three cords (yellow, red and white) to be connected with the television set are provided, and the composite video signal is output from the VTR to the television set through the yellow cord.
FIG. 11A is a waveform view showing various signals included in the composite video signal, and FIG. 11B is an enlarged waveform view showing signals arranged in one horizontal retrace blanking period.
As shown in FIGS. 11A and 11B, one horizontal synchronizing signal B and a color burst signal E are arranged in each horizontal retrace blanking period A, and an image signal is arranged in a period other than the vertical retrace blanking period and the horizontal retrace blanking periods.
An image watched by a viewer is formed according to the image signal. A level range C shown in FIG. 11B indicates a luminance range of the image. As a level (or an electric potential) of the image signal is heightened in the level range C, the luminance of the image becomes heightened, and the image approaches the white color. In contrast, as a level of the image signal is lowered in the level range C, the image approaches the black color. That is, the top level (5 V) in the level range C corresponds to the white color, and the bottom level in the level range C corresponds to the black color and is called a pedestal level. The pedestal level is fixed. Also, in cases where a level of the image signal is placed between the top and bottom levels, the image becomes gray, and the luminance of the image changes with the level of the image signal.
The color of the image is determined by a phase difference between the color burst signal E and the image signal. A detail description of the color determination is omitted.
In addition, to indicate the horizontal synchronizing signal Hsync and the vertical synchronizing signal Vsync, a ground level (GND level) set to 0 V is used.
The electron beam is returned from the right side to the left side of the viewer during each horizontal retrace blanking period (refer to FIG. 10A and FIG. 10B) when the viewer watches the image plane, and a horizontal synchronization of the electron beam is performed during the beam returning period according to the horizontal synchronizing signal. Also, the electron beam is returned from the bottom to top (refer to FIG. 10A and FIG. 10B) during the vertical retrace blanking period corresponding to a period of the horizontal scanning lines which are numbered from No. 1 to No. 21.5 for the odd field and are numbered from No. 262.5 to No. 284 for the even field, and a vertical synchronization of the electron beam is performed during the beam returning period according to the vertical synchronizing signal.
The odd and even fields can be distinguished by the phase relationship of the vertical and horizontal synchronizing signals. That is, the horizontal synchronizing signal and the vertical synchronizing signal have the same phase in case of the odd field, and the phase of the horizontal synchronizing signal is opposite to the phase of the vertical synchronizing signal in case of the even field.
FIG. 12 is a constitutional view showing a conventional video signal producing apparatus.
As shown in FIG. 12, a conventional video signal producing apparatus is composed of
a video input terminal 1 for receiving a composite video signal indicating a video image from a VTR,
an oscillating circuit 8 for generating a main clock signal,
a microcomputer-for-television 9 for producing a composite video signal indicating an on-screen display (hereinafter, called OSD) character such as a channel number or a composite video signal indicating a test pattern according to the main clock signal generated by the oscillating circuit 8, outputting the composite video signal of the test pattern indicated by two port output levels (a pattern output level fixed to 5 V and the ground level 0 V), and outputting the composite video signal of the OSD character as a red (R) signal, a green (G) signal and a blue (B) signal indicated by two levels (0 V and 5 V),
a pair of patterned resistors 16 and 17, serially connected with each other, for adding the pedestal level (Vp) to the composite video signal of the test pattern output from the microcomputer-for-television 9,
a selector 2 for selecting the composite video signal received by the video input terminal 1 or the composite video signal of the test pattern prepared by the microcomputer-for-television 9 and the resistors 16 and 17 according to a first selector control signal output from the microcomputer-for-television 9,
an antenna 3 for receiving broadcasting images from a broadcasting station,
a tuner 4 for selecting a desired broadcasting image of a desired channel and outputting a composite video signal of the desired broadcasting image,
a selector 5 for selecting the composite video signal selected in the selector 2 or the composite video signal output from the tuner 4 according to a second selector control signal output from the microcomputer-for-television 9,
a video processing circuit 6 for converting the composite video signal selected in the selector 5 into a video signal, demultiplexing horizontal synchronizing signals Hsync and a vertical synchronizing signal Vsync from the composite video signal for each field in cases where the composite video signal sent from the video input terminal 1 or the tuner 4 is selected in the selector 5, sending the horizontal synchronizing signals Hsync and the vertical synchronizing signal Vsync to the microcomputer-for-television 9 in synchronization with the horizontal synchronizing signals Hsync and the vertical synchronizing signal Vsync multiplexed in the video signal and mixing the R, G and B signals of the OSD character output from the microcomputer-for-television 9 with the video signal, and
a Braun tube 7 for displaying the desired broadcasting image or the video image according to the video signal produced in the video processing circuit 6, displaying the test pattern according to the video signal to adjust the Braun tube 7 and displaying the OSD character with the desired broadcasting image or the video image according to the R, G and B signals mixed with the video signal in the video processing circuit 6.
The microcomputer-for-television 9 is composed of
a central processing unit (CPU) 10 for controlling constitutional elements of the microcomputer-for-television 9,
a composite video signal outputting circuit 11, having a patterned private circuit corresponding to the test pattern, for determining a timing of a field corresponding to the test pattern, a timing of horizontal scanning lines corresponding to the test pattern, a timing of the horizontal retrace blanking period, a timing of the vertical retrace blanking period, a timing of the horizontal synchronizing signal and a timing of the vertical synchronizing signal in the patterned private circuit according to the main clock signal generated in the oscillating circuit 8 under the control of the CPU 10, producing the composite video signal indicating the test pattern from the timings produced in the private circuit,
a terminal output control circuit 12 for outputting the first and second selector control signal under the control of the CPU 10 to the selectors 2 and 5,
a OSD character output clock circuit 13 for generating an OSD character output clock signal indicating a display period of the OSD character according to a display instruction sent from the CPU 10, and
an OSD circuit 14, having an OSD output circuit 15 and an internal read only memory (ROM), for receiving the display instruction of the OSD character from the CPU 10, reading out a dot pattern of the OSD character from the internal ROM according to the display instruction and outputting the dot pattern of the OSD character as the R, G and B signals from R, G and B terminals of the OSD output circuit 15 in synchronization with the OSD character output clock generated by the OSD character output clock circuit 13 and the horizontal synchronizing signals Hsync and the vertical synchronizing signal Vsync send from the video processing circuit 6.
FIG. 13 is a constitutional view of the OSD output circuit 15.
As shown in FIG. 13, the OSD output circuit 15 is composed of an R output circuit 15a, having a switch, for selecting a Vcc terminal set to 5 V or a GND terminal set to 0V in the switch according to an output control signal and outputting the R signal indicating a dot pattern of the OSD character, of which a red portion is set to 5 V, from the R terminal,
a G output circuit 15b, having a switch, for selecting a Vcc terminal set to 5 V or a GND terminal set to 0V in the switch according to the output control signal and outputting the G signal indicating a dot pattern of the OSD character, of which a green portion is set to 5 V, from the G terminal, and
a B output circuit 15c, having a switch, for selecting a Vcc terminal set to 5 V or a GND terminal set to 0V in the switch according to the output control signal and outputting the B signal indicating a dot pattern of the OSD character, of which a blue portion is set to 5 V, from the B terminal.
In the above configuration, an operation of the conventional video signal producing apparatus is described.
When a user uses the Braun tube 7, because the user does not generally adjust the Braun tube 7, the selector 2 is preset to select a composite video signal received by the video input terminal 1. Therefore, the composite video signal of the VTR or a composite video signal of a television program sent from the broadcasting station is selected by the selector 5 according to a user""s selection and is input to the video processing circuit 6. In the circuit 6, the composite video signal is converted into a video signal, and a video image or a desired broadcasting image of the television program is displayed on the Braun tube 7 according to the video signal.
Also, horizontal synchronizing signals Hsync and a vertical synchronizing signal Vsync are demultiplexed from the composite video signal for each field in the video processing circuit 6, and the horizontal synchronizing signals Hsync and the vertical synchronizing signal Vsync are sent to the OSD circuit 14 of the microcomputer for-television 9 in synchronization with the horizontal synchronizing signals Hsync and the vertical synchronizing signal Vsync multiplexed in the video signal.
In cases where the user desires to display an OSD character such as a channel number xe2x80x9c5xe2x80x9d on the upper right side of the Braun tube 7 (refer to the Braun tube 7 shown in FIG. 12), the user inputs an instruction to a television set, and a display instruction of the OSD character is sent from the CPU 10 to the OSD circuit 14 and the OSD character output clock circuit 13. In the circuit 13, an OSD character output clock signal indicating a display period of the OSD character is generated and is sent to the OSD circuit 14.
In the OSD circuit 14, a dot pattern of the OSD character is read out from the internal ROM according to the display instruction and is output to the video processing circuit 6 in synchronization with the OSD character output clock signal, the horizontal synchronizing signals Hsync and the vertical synchronizing signal Vsync. In detail, because specific information such as a display position of the OSD character, a display size of the OSD character an da display color of the OSD character is included in the display instruction, the numbers of the horizontal scanning lines corresponding to the dot pattern of the OSD character are determined according to the specific information on the basis of the horizontal synchronizing signals Hsync and the vertical synchronizing signal Vsync sent from the video processing circuit 6, and the dot pattern of the OSD character is output to the video processing circuit 6 in the display period of the OSD character indicated by the OSD character output clock signal in synchronization with the horizontal synchronizing signals Hsync and the vertical synchronizing signal Vsync.
Thereafter, in the video processing circuit 6, the R, G and B signals indicating the dot pattern of the OSD. character are mixed with the video signal. Thereafter, the OSD character is displayed with the desired broadcasting image or the video image on the Braun tube 7.
FIG. 14 shows an output timing of a dot pattern of a channel number xe2x80x9c5xe2x80x9d (indicated by an arrow) corresponding to one horizontal scanning line indicated by one horizontal synchronizing signal.
As shown in FIG. 14, when the electron beam is moved to the upper right side of an image displayed on the Braun tube 7, a G signal indicating a dot pattern (that is, a string of dots) of a channel number xe2x80x9c5xe2x80x9d representing the OSD character is only output from the G terminal to the video processing circuit 6, and a string of green dots is displayed on the upper right side of the image for each horizontal scanning line. Therefore, the channel number xe2x80x9c5xe2x80x9d indicated by green is displayed with the image.
Next, when the Braun tube 7 is manufactured in a factory, it is required to adjust the Braun tube 7 in the factory. In this case, the selector 2 is set to select a composite video signal sent from the composite video signal outputting circuit 11, and the terminal output control circuit 12 is set under the control of the CPU 10 to make the selector 5 select the composite video signal sent from the selector 2. Thereafter, a composite video signal of a test pattern is produced in the composite video signal outputting circuit 11 and the resistors 16 and 17.
In detail, the composite video signal indicating the test pattern is produced by inputting the main clock signal generated in the oscillating circuit 8 to the private circuit patterned in the composite video signal outputting circuit 11. Therefore, the composite video signal, in which signals are always multiplexed at fixed timings, can be obtained. In this case, the composite video signal are indicated by the pattern output level fixed to 5 V and the GND level (0 V). However, because the pedestal level having a fixed electric potential is required for the composite video signal to indicate the black color, the horizontal synchronizing signals and the vertical synchronizing signal, the pedestal level of a fixed electric potential is added to the composite video signal by using the resistors 16 and 17 of resistances R1 and R2. In detail, when the pedestal level is set to the composite video signal, the port of the microcomputer-for-television 9 is set to a high impedance condition to obtain an intermediate electric potential VP from the pattern output level fixed to 5 V. Therefore, the pattern output level of the composite video signal set in the composite video signal output circuit 11 is changed to the pedestal level equal to the intermediate level Vp.
Vp={R2/(R1+R2)}*5xe2x80x83xe2x80x83(V)
Because the pedestal level Vp is obtained from the fixed level 5 V, the pedestal level can be fixed.
Also, when it is desired to remain the composite video signal to the pattern output level or the GND level, the high impedance condition of the port is cancelled.
Thereafter, the composite video signal indicated by the pattern output level (5 V), the GND level (0 V) and the pedestal level (Vp) is sent to the video processing circuit 6 through the selectors 2 and 5 and is converted into a video signal in the video processing circuit 6. Thereafter, the test pattern indicated by the video signal is displayed on the Braun tube 7, in the same manner as the display of the broadcasting image. Therefore, a manufacturer can adjust the Braun tube 7 while viewing the test pattern.
FIG. 15 is an explanatory view showing a cross-hatched pattern representing the test pattern and a waveform of a composite video signal of the cross-hatched pattern corresponding to one horizontal scanning line according to the NTSC.
As shown in FIG. 15, the composite video signal is indicated by the pattern output level fixed to 5 V, the GND level (0 V) and the pedestal level (Vp), and a cross-hatched pattern indicated by black and white (or one brightest color) is shown on the Braun tube 7.
Accordingly, because the main clock signal generated in the oscillating circuit 8 is input to the private circuit patterned in the composite video signal output circuit 11, the composite video signal of the test pattern, of which display modes such as shape, position, size and color are predetermined, is produced, and the test pattern can be reliably displayed on the Braun tube 7.
Also, because the pedestal level is added to the composite video signal indicated by the pattern output level fixed to 5 V and the GND level (0 V) by using the resistors 16 and 17 and controlling the port output level of the composite video signal in the micro computer for-television 9, the test pattern indicated by a color of the highest luminance degree and the black color can be displayed on the Braun tube 7.
However, because the private circuit is required and the resistors 16 and 17 are required to be patterned, there is a drawback that a size of the video signal producing apparatus is enlarged and a manufacturing cost of the video signal producing apparatus is increased.
Also, though the composite video signal having three output levels can be output from the composite video signal output circuit 11 and the resistors 16 and 17, because it is required to set the pedestal level to the fixed level Vp, the pattern output level cannot be adjusted to an arbitrary level. That is, the pattern output level is fixed to 5 V. Therefore, there is another drawback that a color level (or the luminance) of the test pattern indicated by the pattern output level (5 V) cannot be adjusted.
Also, because the test pattern is predetermined in the patterned private circuit, setting conditions (for example, cross-hatched pattern or upper-right side) of the display modes (for example, shape or position) of the test pattern is fixed. Therefore, there is another drawback that the setting conditions of the display modes of the test pattern cannot be easily changed.
To solve the above drawbacks, a main object of the present invention is to provide a video signal producing apparatus which has a small size and is obtained at a low cost. Also, the main object of the present invention is to provide a video signal producing method performed in the apparatus.
A first subordinate object of the present invention is to provide video signal producing apparatus and method in which the luminance of a test pattern is minutely adjusted.
A second subordinate object of the present invention is to provide video signal producing apparatus and method in which the setting conditions of the display modes of the test pattern are easily changed.
To achieve the main object, a video signal producing apparatus comprising:
synchronizing signal generating means for generating a plurality of horizontal synchronizing signals and a vertical synchronizing signal matching with a videosignal broadcasting standard;
setting means for setting a display mode of one or more characters to set the display mode of a test pattern composed of the characters; and
video signal producing means for producing a composite video signal of the test pattern satisfying the display mode set by the setting means according to the horizontal synchronizing signals and the vertical synchronizing signal generated by the synchronizing signal generating means.
When a manufacturer or a user desires to adjust a display apparatus, it is required to send a composite video signal of a test pattern to the display apparatus and to display the test pattern on an image plane of the display apparatus as a test according to the composite video signal.
In the above configuration, a plurality of horizontal synchronizing signals and a vertical synchronizing signal matching with a video signal broadcasting standard to which the display apparatus is adapted are generated by the synchronizing signal generating means for each field. Also, a display mode (for example, shape, position, size, color or luminance degree) of a type of character is set by the setting means, so that the display mode of the test pattern composed of characters of the same type is set. Thereafter, a composite video signal of the test pattern satisfying the display mode is produced according to the horizontal synchronizing signals and the vertical synchronizing signal by the video signal producing means.
Accordingly, because the composite video signal of the test pattern satisfying the display mode can be produced without using any private circuit, the video signal producing apparatus can be produced in a small size. Also, because the video signal producing apparatus is produced in a small size, the cost of producing the video signal producing apparatus can be suppressed.
It is preferred that the display mode of the characters set by the setting means be a display shape of the characters, a display position of each character, a display size of the characters, a display color of each character or the luminance of each character.
In this invention, a display shape (for example, cross-hatched pattern obtained by combining a plurality of squared loops), a position (for example, upper-right side), a size, a color (for example, red) and/or a luminance degree of the test pattern composed of the characters can be set. In particular, a color brightness of the test pattern can be specified by setting the color and luminance.
To achieve the first subordinate object, it is also preferred that the luminance of the characters be set to a particular luminance degree by the setting means as a setting condition of the display mode of the characters, and the video signal producing means comprise an output circuit for selecting a particular electric potential value corresponding to the particular luminance degree of the characters from three or more electric potential values including an electric potential value corresponding to black and an electric potential value corresponding to white and setting the electric potential of a pattern signal corresponding to the characters in the composite video signal to the particular electric potential value.
In this invention, because a particular electric potential value corresponding to the particular luminance degree of the characters is selected from three or more electric potential values, the brightness of the test pattern displayed on the display apparatus can be selected from one or more intermediate brightness degrees other than brightness degrees corresponding to white and black. Accordingly, the brightness (or the luminance) of the test pattern displayed can be minutely adjusted.
It is also preferred that the video signal producing apparatus further comprises:
renewing means for controlling the synchronizing signal generating means to generate a plurality of horizontal synchronizing signals and a vertical synchronizing signal matching with a new video signal broadcasting standard in place of the horizontal synchronizing signals and the vertical synchronizing signal matching with the video signal broadcasting standard.
In the above configuration, one video signal broadcasting standard adapted in the video signal producing apparatus is renewed to a new video signal broadcasting standard such as NTSC, PAL system, Sequential Colors A Memoire (SECAM) or the like. Therefore, even though the display apparatus adapted to one video signal broadcasting standard is changed to a new display apparatus adapted to the new video signal broadcasting standard, the video signal broadcasting standard can be easily renewed to the new video signal broadcasting standard matching with the new display apparatus.
To achieve the second subordinate object, it is also preferred that the video signal producing apparatus further comprises:
changing means for controlling the setting means to set the display mode of the characters to a new setting condition in place of a predetermined setting condition of the display mode.
In the above configuration, even though the display mode (for example, position) of the characters is set to the predetermined setting condition (for example, upper-right side), the predetermined setting condition of the display mode can be changed to a new setting condition (for example, upper-left side). Accordingly, setting conditions of display modes (for example, shape, position, size, color or luminance) for the test pattern can be easily changed.
To also achieve the main object, a video signal producing method, comprising the steps of:
generating a plurality of horizontal synchronizing signals and a vertical synchronizing signal matching with a video signal broadcasting standard;
setting a display mode of one or more characters to set the display mode of a test pattern composed of the characters; and
producing a composite video signal of the test pattern satisfying the display mode according to the horizontal synchronizing signals and the vertical synchronizing signal.
In the above steps, the video signal producing method is useful for the video signal producing apparatus manufactured in a small size and at a low cost.
It is preferred that the step of setting the display mode of the characters include the step of:
setting a display shape of the characters, a display position of each character, a display size of the characters, a display color of each character or the luminance of each character as the display mode of the characters.
In the above step, a color brightness of the test pattern can be specified by setting the color and luminance.
To also achieve the first subordinate object, it is also preferred that the step of setting the display mode of the characters include:
setting the luminance of the characters to a particular luminance value as a setting condition of the display mode of the characters, and
the video signal producing method further comprising the steps of:
selecting a particular electric potential value corresponding to the particular luminance degree of the characters from three or more electric potential values including an electric potential value corresponding to black and an electric potential value corresponding to white; and
setting the electric potential of a pattern signal corresponding to the characters in the composite video signal to the particular electric potential value.
In the above steps, the brightness (or the luminance) of the test pattern displayed can be minutely adjusted.
It is also preferred that the step of generating the horizontal synchronizing signals and the vertical synchronizing signal matching with the video signal broadcasting standard includes the steps of:
renewing the video signal broadcasting standard to a new video signal broadcasting standard; and
generating a plurality of horizontal synchronizing signals and a vertical synchronizing signal matching with the new video signal broadcasting standard in place of the horizontal synchronizing signals and the vertical synchronizing signal matching with the video signal broadcasting standard to produce a composite video signal of the test pattern according to the horizontal synchronizing signals and the vertical synchronizing signal matching with the new video signal broadcasting standard.
In the above steps, the video signal broadcasting standard can be easily renewed to the new video signal broadcasting standard matching with the new display apparatus.
To also achieve the second subordinate object, it is preferred that the step of setting the display mode of the characters include the steps of:
changing a predetermined setting condition of the display mode of the characters to a new setting condition; and
setting the display mode of the characters to the new setting condition in place of the predetermined setting condition to produce a composite video signal of the test pattern satisfying the display mode set to the new setting condition.
In the above steps, setting conditions of display modes (for example, shape, position, size, color or luminance) for the test pattern can be easily changed.
Also, it is applicable that the test pattern be obtained by combining the characters having the same shape set by the setting means.
Also, it is applicable that the step of setting the display mode of the characters include the steps of:
setting the characters to the same shape; and
combining the characters having the same shape to produce the test pattern.
In this invention, because the test pattern is obtained by combining the characters having the same shape, even though a shape of the test pattern is complicated, the test pattern can be easily obtained by combining the characters having the same simple shape. Therefore, a small-sized video signal producing apparatus can be obtained at a low cost.